I want to set all of my http headers responses to something like this:

response.headers["X-Frame-Options"] = "SAMEORIGIN"

I checked this question, but it only changes the header for one specific controller. I want to change all of my headers maybe in "before_request" function similar to the following logic. How can I do that?

@app.before_request
def before_request():
    # response.headers["X-Frame-Options"] = "SAMEORIGIN"

Set the header in a @app.after_request() hook, at which point you have a response object to set the header on:

@app.after_request
def apply_caching(response):
    response.headers["X-Frame-Options"] = "SAMEORIGIN"
    return response

The flask.request context is still available when this hook runs, so you can still vary the response based on the request at this time.